SELECT 
  1 
FROM 
  cscart_lock_keys 
WHERE 
  key_id = 'fa6758ccfcef4e4d806c71500439db1de5d505de990fe3be0d7185cf41523de9' 
  AND token = 'k9oWRnfLCIjMqprL4HozHA+Osg/gvGSqTN2lesEvikU=' 
  AND expiry_at > UNIX_TIMESTAMP(NOW())

Query time 0.00018

JSON explain

{
  "query_block": {
    "select_id": 1,
    "message": "no matching row in const table"
  }
}